Remove leftovers of platformName and platformStatic in test data

Drop unnecessary imports, rename some tests

compiler/testData/diagnostics/testsWithStdLib/duplicateJvmSignature/jvmStaticInClassObject.kt

@@ -0,0 +1,9 @@
+open class Base {
+    fun foo() {}
+}
+
+class Derived : Base() {
+    companion object {
+        <!ACCIDENTAL_OVERRIDE!>@JvmStatic fun foo()<!> {}
+    }
+}